A highly precise time synchronization of subscribers in communication systems is considered the basis of many future real-time applications in the field of automation and measuring technology. Precise time information in data terminals (subscribers) allows the realization of distributed, highly synchronous processes such as they are increasingly demanded in motion control applications, in measuring and control technology or in mechanical engineering. Time synchronization is thus a prerequisite for virtually all real-time applications in communication systems.
The IEEE1588 standard is often used for cyclical time synchronization. It bears the title “Precision Clock Synchronization Protocol for Networked Measurement and Control Systems”, abbreviated to “PTP” for “Precision Time Protocol”. This standard defines a method for synchronizing many spatially distributed real-time clocks that are interconnected via a package-compatible network such as the Ethernet. According to PTP, one subscriber establishes itself as master clock and transmits a first software-generated sync-telegram and then a follow-up telegram to the other subscribers (slaves) indicating the precise time of the first telegram. On the basis of the first telegram and the follow-up telegram as well as its own clock, the receiver-subscriber is able to calculate the time difference between its own clock and the master clock and thus carry out a synchronization. This synchronization process repeats itself in the sync-telegram cycle.
Another known method is the cyclical transmission of an item of absolute time information (such as SYNAX network) for time synchronization at a slight time delay in the transmission.
The current solutions, some of which use complicated mechanisms, cyclically synchronize the time information in the subscribers by active transmission of an item of absolute time information. The present invention provides a simplified time-synchronization method in cyclically operating communication systems.